The long-term objective of this research program is to enhance the effectiveness of treatments for patients with co-occurring AUD-PTSD by advancing knowledge on models and mechanisms that explain the association between alcohol misuse and [unreadable] PTSD. Long-term natural course data on alcohol use/abuse and PTSD can help identify subgroups of patient with potentially different etiologies and/or maintaining factors, which can lead to further theory development/refinement and improved specificity of treatments. Limited work exists on methodologies that can address these issues. This research seeks to evaluate the reliability and validity of a widely used, established psychiatric interview schedule, the Longitudinal Interval Follow-Up Evaluation (LIFE), which can provide detailed study (i.e., weekly status reports) of the course of PTSD over long time periods (i.e., years) among AUD patients. In addition, this project seeks to provide an initial test of two course models/potential subgroups of AUD-PTSD. A total of 152 men and women in outpatient treatment for AUD will be assessed at treatment entry and at a 6-month follow-up. At treatment entry, participants will complete structured clinical interviews of AUD and PTSD. At the 6-month follow-up, [unreadable] participants will complete the LIFE, measuring weekly PTSD symptom reports during the time between treatment entry and follow-up. Daily alcohol consumption and other drug use will also be assessed during this time period. To assess reliability of the LIFE, two designs will be used: (a) inter-rater, consisting of videotaped or in-person concurrent ratings; and (b) test-retest, consisting of one-week test-retest ratings by different interviewers. To assess validity, a subsample will complete prospective bi-weekly LIFE PTSD symptom assessments, which will be compared to retrospectively collected LIFE [unreadable] PTSD symptom assessment for the 6-month follow-up. At study completion, patients will be asked about their experiences, perceptions, and satisfaction with the LIFE study protocol. Based on findings generated by this study, the LIFE will be further refined and readied for larger-scale long-term studies on the naturalistic course of PTSD and alcohol use disorder comorbidity, with a focus on identification of patient subgroups that can inform theory and treatment development. [unreadable] [unreadable] [unreadable]